Ametek ORTEC 480 Service manual

Model 480
Pulser
Operating and Service Manual
Printed in U.S.A. ORTEC® Part No. 733390 0815
801 South Illinois Avenue Manual Revision C
Oak Ridge, Tennessee 37830
United States of America

Advanced Measurement Technology, Inc.
a/k/a/ ORTEC®, a subsidiary of AMETEK®, Inc.
WARRANTY
ORTEC* warrants that the items will be delivered free from defects in material or workmanship. ORTEC makes
no other warranties, express or implied, and specifically NO WARRANTY OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
ORTEC’s exclusive liability is limited to repairing or replacing at ORTEC’s option, items found by ORTEC to
be defective in workmanship or materials within one year from the date of delivery. ORTEC’s liability on any
claim of any kind, including negligence, loss, or damages arising out of, connected with, or from the
performance or breach thereof, or from the manufacture, sale, delivery, resale, repair, or use of any item or
services covered by this agreement or purchase order, shall in no case exceed the price allocable to the item or
service furnished or any part thereof that gives rise to the claim. In the event ORTEC fails to manufacture or
deliver items called for in this agreement or purchase order, ORTEC’s exclusive liability and buyer’s exclusive
remedy shall be release of the buyer from the obligation to pay the purchase price. In no event shall ORTEC be
liable for special or consequential damages.
Quality Control
Before being approved for shipment, each ORTEC instrument must pass a stringent set of quality control tests
designed to expose any flaws in materials or workmanship. Permanent records of these tests are maintained for
use in warranty repair and as a source of statistical information for design improvements.
Repair Service
If it becomes necessary to return this instrument for repair, it is essential that Customer Services be contacted
in advance of its return so that a Return Authorization Number can be assigned to the unit. Also, ORTEC must
be informed, either in writing, by telephone [[phone]] or by facsimile transmission [[phone]],
of the nature of the fault of the instrument being returned and of the model, serial, and revision ("Rev" on rear
panel) numbers. Failure to do so may cause unnecessary delays in getting the unit repaired. The ORTEC
standard procedure requires that instruments returned for repair pass the same quality control tests that are used
for new-production instruments. Instruments that are returned should be packed so that they will w ithstand
normal transit handling and must be shipped PREPAID via Air Parcel Post or United Parcel Service to the
designated ORTEC repair center. The address label and the package should include the Return Authorization
Number assigned. Instruments being returned that are damaged in transit due to inadequate packing will be
repaired at the sender's expense, and it will be the sender's responsibility to make claim with the shipper.
Instruments not in warranty should follow the same procedure and ORTEC will provide a quotation.
Damage in Transit
Shipments should be examined immediately upon receipt for evidence of external or concealed damage. The
carrier making delivery should be notified immediately of any such damage, since the carrier is normally liable
for damage in shipment. Packing materials, waybills, and other such documentation should be preserved in order
to establish claims. After such notification to the carrier, please notify ORTEC of the circumstances so that
assistance can be provided in making damage claims and in providing replacement equipment, if necessary.
Copyright © 2002, Advanced Measurement Technology, Inc. All rights reserved.
*ORTEC®is a registered trademark of Advanced Measurement Technology, Inc. All other trademarks used
herein are the property of their respective owners.

iii
CONTENTS
WARRANTY...................................................................... ii
SAFETYINSTRUCTIONSANDSYMBOLS. ............................................... iv
SAFETY WARNINGS AND CLEANING INSTRUCTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
1. DESCRIPTION.................................................................. 1
1.1. GENERAL. .............................................................. 1
1.2. BASICFUNCTION.......................................................... 1
2. SPECIFICATIONS. .............................................................. 2
2.1. PERFORMANCE. ......................................................... 2
2.2. CONTROLS. ............................................................. 2
2.3. OUTPUTS................................................................ 2
2.4. ELECTRICALANDMECHANICAL. ............................................. 2
3. INSTALLATION.................................................................. 2
3.1. GENERAL. .............................................................. 2
3.2. CONNECTIONTOPOWER. .................................................. 2
4. OPERATION. .................................................................. 3
4.1. PANELCONTROLS. ....................................................... 3
4.2. INITIAL TESTING AND OBSERVATION OF PULSE WAVEFORMS. . . . . . . . . . . . . . . . . . . . . . . 3
4.3. CONNECTORDATA........................................................ 3
4.4. TYPICAL OPERATING CONSIDERATIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. MAINTENANCE................................................................. 7
5.1. TESTING PERFORMANCE OF THE PULSER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. ADJUSTMENT OF DECAY TIME OF OUTPUT PULSE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3. TABULATEDTESTPOINTVOLTAGES........................................... 8
5.4. SUGGESTIONS FOR TROUBLESHOOTING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

iv
SAFETY INSTRUCTIONS AND SYMBOLS
This manual contains up to three levels of safety instructions that must be observed in order to avoid personal
injury and/or damage to equipment or other property. These are:
DANGER Indicates a hazard that could result in death or serious bodily harm if the safety instruction is
not observed.
WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not observed.
CAUTION Indicates a hazard that could result in property damage if the safety instruction is not
observed.
Please read all safety instructions carefully and make sure you understand them fully before attempting to
use this product.
In addition, the following symbol may appear on the product:
ATTENTION–Refer to Manual
DANGER–High Voltage
Please read all safety instructions carefully and make sure you understand them fully before attempting to
use this product.

v
DANGER Opening the cover of this instrument is likely to expose dangerous voltages. Disconnect the
instrument from all voltage sources while it is being opened.
WARNING Using this instrument in a manner not specified by the manufacturer may impair the protection
provided by the instrument.
CAUTION To prevent moisture inside of the instrument during external cleaning, use only enough liquid
to dampen the cloth or applicator.
SAFETY WARNINGS AND CLEANING INSTRUCTIONS
Cleaning Instructions
To clean the instrument exterior:
!Unplug the instrument from the ac power supply.
!Remove loose dust on the outside of the instrument with a lint-free cloth.
!Remove remaining dirt with a lint-free cloth dampened in a general-purpose detergent and water solution.
Do not use abrasive cleaners.
!Allow the instrument to dry completely before reconnecting it to the power source.

vi

1
ORTEC MODEL 480
PULSER
1. DESCRIPTION
1.1. GENERAL
The ORTEC 480 is a modular pulse generator
designed to simulate the detection of a nuclear
particle reaction in a solid-state or scintillation
detector. The unit features good stability as a
function of temperature and time, 1% overall
accuracy, and a front panel CaI control which
enables it to be calibrated to read directly in terms of
equivalent energy deposited in a detector. The
pulses are generated with a mercury relay switch
whose frequency is the frequency of the ac line. The
instrument has an internal stable reference voltage
that is effectively independent of the modular power
supply and ac line voltage changes. The unit has
four attenuator toggle switches for a maximum
attenuation of 1000:1. The direct output precedes
the attenuator switch and provides a means of
stable oscilloscope triggering. Two terminators are
provided with the 480: a charge terminator and a
100Ùvoltage terminator. The use of a charge
terminator allows the voltage output pulse of the 480
to be converted to a charge pulse for subsequent
amplification by a charge-sensitive preamplifier. A
holder is provided on the rear panel to store the
charge terminator when it is not in use.
This instrument is designed to meet the
recommended interchangeability standards of US
DOE Report TID-20893 (Rev.). An ORTEC
4001/4002 Series Bin and Power Supply provides all
necessary power through the rear module power
connector. The ORTEC 400 Series is designed so
that it is not poss ible to overload the Bin Power
Supply with a full complement of modules in the Bin.
However, this may not be true when the Bin contains
modules of other than ORTEC design. All signal
levels and impedances are compatible with other
modules in the ORTEC 400 Series.
1.2. BASIC FUNCTION
The 480 provides output pulses that are
characterized by a fast rise time and a slow
exponential decay time. These pulses are generated
by charging a capacitor to an internal reference
voltage through a mercury relay and then
discharging the capacitor through the switching
action of the mercury relay into a fixed resistive load.
The use of mercury-wetted relay contacts provides
a very fast rise time, typically less than 5 nsec 10-
90% rise time, with an absolute minimum of contact
bounce or other perturbations of the waveform for
the first few microseconds. The output impedance of
the pulse generator on both the direct and
attenuated output is 100Ù. The direct output
provides a trigger pulse that allows the stable
synchronization of an oscilloscope or other timing
equipment from a signal which does not vary in
amplitude as the attenuators are switched in and
out. The attenuated output has a series of pi-
attenuators between the mercury-wetted relay
contacts and the output BNC connector. This allows
the attenuation of the signal by a fixed amount,
depending upon the particular switch operated in the
series attenuator. The primary purpose of the pulse
generator is to simulate radiation detection signals.
Since the pulses are generated from an
electromechanical device (the mercury-wetted
relay), the frequency of the pulse generator is
correspondingly rather slow, i.e., the frequency of
the ac line.

2
2. SPECIFICATIONS
2.1. PERFORMANCE
Temperature Stability 0.01%/EC, 0 to 50EC.
Line Voltage Stability 0.005% per 10% change in
line voltage.
Ripple and Noise 0.003% of pulse amplitude.
Nonlinearity ±0.25% of full scale.
Rise Time Exponential waveform, <10 nsec (10 to
90%).
Fall Time Exponential decay with 200- or 400-ìsec
time constant (depending on whether or not the
direct output is terminated).
2.2. CONTROLS
Cal 22-turn potentiometer on front panel, covers
>2:1 amplitude span for normalization of Pulse
Height control to read directly in equivalent energy.
Pulse Height Front panel potentiometer, controls
output pulse height from zero volts to the maximum
determined by the Attenuator switches, the CaI
control setting, and the termination load.
Attenuator Front panel switches, provide step
attenuation over 1000:1 range with 1% resistors (X2,
X5, X10, X10).
Off/On Front panel slide switch, allows internal
relay to be driven from the ac line.
Neg/Pos Front panel slide switch, determines
polarity of the output signal.
2.3. OUTPUTS
Atten Front panel BNC connector provides positive
or negative dc-coupled output with an impedance of
100Ù.
Direct Front panel BNC connector provides positive
or negative dc-coupled. 0- to 10-V pulse into a high
impedance and 0- to 5-V max pulse into 100Ù. This
is equivalent to a range of 0- to 220-MeV energy
referred to a silicon detector, when used with
associated charge terminator.
Accessories Included One 100Ùvoltage
terminator and one charge terminator.
2.4. ELECTRICAL AND MECHANICAL
Power Required
+24 V 60 mA; +12 V, 0 mA;
-24 V 60 mA; -12 V, 0 mA.
115 V ac, 8 mA (used only to drive relay).
Weight (Shipping) 4.1 lb (1.86 kg).
Weight (Net) 2.1. lb (0.95 kg).
Dimensions NIM-standard single-width module
(1.25 by 8.714 in.) Per TID-20893 (Rev.).
3. INSTALLATION
3.1. GENERAL
The 480 contains no internal power supply but is
used in conjunction with an ORTEC 4001/4002
Series Bin and Power Supply, which is intended for
rack mounting. Therefore if vacuum tube equipment
is operated in the same rack with the 480, there
must be sufficient cooling air circulating to prevent
any localized heating of the 480 and the associated
Bin and Power Supply. The temperature of
equipment mounted in racks can easily exceed
120EF (50EC) unless precautions are taken. The
480 should not be s ubjected to temperatures in
excess of 120EF.
3.2. CONNECTION TO POWER

3
Always turn off the Bin Power Supply when inserting
or removing modules. The 4001/4002 has test
Points on the Power Supply control Panel to monitor
the dc voltages. When using the 480 outside the
4001/4002, ensure that the power jumper cable
used properly accounts for the Power Supply
grounding circuits provided in the recommended
standards of US DOE TID-20893 (Rev.). Both high-
quality and power-return ground connections are
provided to ensure proper reference voltage
feedback into the Power Supply, and these must be
preserved in remote installations. Care must also be
exercised to avoid ground loops when the module is
operated outside the Bin.
If the 480 should be inserted in a bin that has no ac
voltage dis tribution, the unit will not operate since
the relay is driven from the ac line on pins 33 and
41.
4. OPERATION
4.1. PANEL CONTROLS
Cal A 22-turn potentiometer on the front panel
varies the output pulse height continuously over a
2.5:1 range (approximately) to allow for
normalization of the Pulse Height dial setting.
Pulse Height The Pulse Height potentiometer on
the front panel controls is the output pulse height
from zero volts to the maximum determined by the
Attenuator toggle switches and the termination load.
This 10-turn potentiometer has a calibration linearity
of ±0.25%.
Attenuators Four toggle switches on the front
panel control pi-attenuators in the attenuated output
line; the maximum attenuation is 1000:1. These
switches have an accuracy controlled by 1% metal
film resistors and depend upon the attenuated
output being terminated in 100Ù.
Off/On This front panel slide switch allows the
internal relay to be driven from the ac line. The
frequency of the ac line will be 50 to 60 Hz.
Neg/Pos The Polarity of the output signal will be
either negative (-) or Positive (+) as determined by
the setting of this front panel slide switch.
4.2. INITIAL TESTING AND
OBSERVATION OF PULSE WAVEFORMS
See Section 6.1 for test performance data.
4.3. CONNECTOR DATA
CN 1 The Direct Output BNC connector provides a
dc-coupled output that looks back directly at the
relay and has an output impedance of 100Ù. The
output of this connector provides a constant output
voltage for a given setting of the Puls e Height
control independent of the position of the Attenuator
switches. Output voltage range is from 0 to 5 V
maximum into 100Ùand 0 to 10 V into a high
impedance. The direct output may or may not be
terminated with a 100Ùterminator. If the direct
output is terminated with a 100Ùterminator, the
decay time of the output pulse will change from a
nominal value of 400 ìsec to a value of 200 ìsec.
The polarity of the Direct Output pulse will be either
negative or positive as determined by the Neg/Pos
switch.
CN 2 The Attenuated Output BNC connector
provides a dc-coupled output connector with an
output impedance of 100Ù. The attenuated output
has the Attenuators in series with it. The use of
these switches therefore alters the pulse amplitude
appearing at the attenuated output for a given
setting of the Pulse Height control. The attenuated
output should always be terminated with 100Ù. The
polarity of the output pulse will be determined by the
Neg/Pos switch.
TPI An oscilloscope test point is on the front panel
for monitoring the signal on the Direct Output BNC
connector CN1. This test point has a 470Ùseries
resistor connecting it to CN1.
TP2 An oscilloscope test point is also on the front
panel for monitoring the signal on Attenuated Output

4
Fig. 4.1. Measuring Amplifier and Detector Noise
Resolution.
BNC connector CN2. This tes t point has a 470Ù
series resistor connecting it to CN2.
4.4. TYPICAL OPERATING
CONSIDERATIONS
Charge and Voltage Terminators A charge
terminator that consists of a 100Ùshunt resistor
with a 2-pF series capacitor is supplied for use with
ORTEC charge-sensitive preamplifiers. When this
terminator is used, the maximum output pulse is 5 V
on 10 pC (220 MeV for silicon diode detectors).
When the charge terminator is used to drive a
charge-sensitive preamplifier, a coaxial cable having
an impedance of approximately 100Ù(RG-62/U)
should be used between the pulse generator and
the charge terminator. The terminator should be
located at the input connector of the preamplifier.
The charge terminator may be used with or without
a detector being applied to the input of a
preamplifier. If a detector is connected to the
preamplifier, detector bias must be applied to
reduce the effective detector capacity shunting the
charge-sensitive preamplifier input. Also, with the
charge terminator used simultaneously with a
semiconductor detector, it must be remembered that
the charge terminator effectively shunts the detector
with approximately 2.5 pF of shunt capacity, which
will correspondingly degrade the signal-to-noise
performance of the preamplifier.
For voltage drive to an instrument under test, use
coaxial cable having an impedance of
approximately 100Ù(RG-62/U) between the pulse
generator and the instrument under test. Place a
100Ùtermination at the instrument end of the cable
in shunt with the input of the instrument.
Calibrating the Test Pulser and Amplifier for
Energy Measurements The 480 may easily be
calibrated so that the maximum Pulse Height dial
reading (1000 divisions) is equivalent to a specific
MeV loss in a radiation detector. The procedure is
as follows:
1. Connect the detector to be used to the
spectrometer system, i.e., preamplifier, main
amplifier, and biased amplifier.
2. Allow particles from a source of known energy
(alpha particles, for example) to fall on the detector.
3. Adjust the amplifier gains and the bias level of the
biased amplifier to give a suitable output pulse.
4. Set the pulser Pulse Height potentiometer at the
energy of the alpha particles striking the detector
(e.g., for a 5.1-MeV alpha particle, set the dial at 510
divisions).
5. Turn on the pulser; use the CaI potentiometer and
the Attenuator switches to set the output due to the
pulser to the same pulse height and shape as the
pulse obtained in step 3.
Amplifier Noise and Resolution Measurements
As shown in Fig. 4.1, a preamplifier, amplifier, pulse
generator, oscilloscope, and wide-band rms
voltmeter, such as the Hewlett- Packard 400D, are
required for this measurement. Connect a suitable
capacitor to the input to simulate the detector
capacitance desired. To obtain the resolution spread
due to noise:
1. Measure the rms noise voltage (Erms) at the linear
amplifier output.
2. Turn on the 480 and adjust the linear amplifier
output to any convenient readable voltage, Eo, as
determined by the oscilloscope.
The full width at half maximum (FWHM) resolution
spread due to the amplifier noise is then N(FWHM)
= 2.66 Erms Edial/Eo, where Edial is the pulser dial
reading in MeV, and the factor 2.66 is the correction
factor for rms to full widt h at half maximum (2.35)
and noise to rms meter correction (1.13) for average
indicating voltmeters such as the Hewlett-Packard
400D. The resolution spread will depend upon the
total input capacity, since the capacitance degrades
the signal-to-noise ratio much faster than the noise.
A typical resolution s pread versus external input
capacitance in the RC mode is shown in Fig. 4.2.
Amplifier Noise a nd Resolution Measurements

5
Fig. 4.2. Resolution Spread vs External Input Capacity.
Fig. 4.4. Amplifier and Detector Noise v s Bias
Voltage.
Fig. 4.3. Measuring Resolution with a Pulse Height
Analyzer.
Using a Pulse Height Analyzer Probably the most
convenient method of making resolution
measurements is with a pulse height analyzer as
shown by the setup illustrated in Fig. 4.3. The
amplifier noise resolution spread can be measured
correctly with a pulse height analyzer and the 480 as
follows:
1. Select the energy of interest with the 480, and set
the linear amplifier and biased amplifier gain and
bias level controls so that the energy is in a
convenient channel of the analyzer.
2. Calibrate the analyzer in keV per channel, using
the purser. (Full scale on the pulser dial is 10 MeV
when calibrated as described in "Calibrating the Test
Pulser and Amplifier for Energy Measurements."

6
Fig. 4.5. Measuring Linearity by the Null-Balance Method.
3. Then obtain the amplifier noise resolution spread
by measuring the FWHM of the pulser spectrum.
The detector noise resolution spread for a given
detector bias can be determined in the same
manner by connecting a detector to the preamplifier
input. The amplifier noise resolution spread, of
course, must be subtracted. The detector noise will
vary with detector size and bias conditions as
indicated in Fig. 4.4 and possibly with ambient
conditions.
Amplifier Linearity Measurements The
measurement of amplifier linearity c an be quickly
and simply done by utilizing the method outlined in
Fig. 4.5. The method consists of bucking out two
voltage signals from low-impedance sources and
measuring the amplitude differential at a null point.
The following conditions of Fig. 4.5 should be
considered when linearity measurements are made.
The output impedance of the Direct Output must be
100Ù. The amplifier must be set in the inverting
mode of operation; i.e., for the negative input shown,
the amplifier must produce a positive Output Pulse.
The impedance seen from point A to ac, or signal,
ground via point C should be equal to the
impedance seen from point A to ac, or signal,
ground via point B. The diodes D should be
germanium units with high gm. The diodes can be
replaced with high-frequency germanium transistors
with the base connected to the collector so that the
emitter-base functions as the diode. Transistors
suitable for this test include 2N779, 2N964, 2N976,
2N2048. The diodes serve as bipolar voltage clamps
to limit the voltage swing at point A to the forward
voltage drop across the diodes. The diode-resistor
network should be constructed so as to minimize the
stray capacitance around this network. The network
should be physically located on the oscilloscope
input connector for the same reason.
Initially the output of the Pulser and amplifier should
be set for 10 V. This should be measured with cars,
and consideration should be given for the output
impedance of both the Pulser and amplifier. By
observing the waveshape at point A (Fig. 4.5), the
fine gain of the amplifier and the attenuation controls
should be adjusted until a null is obtained between
time t1and t2. At null, the sensitivity of the
oscilloscope should be set to 10 mV/cm for best

7
resolution of the null measurement.
The actual measurement of linearity is
accomplished by dialing the Pulse Height dial to 0,
resulting in the amplifier output being reduced to
zero. Since the Pulser supplies s ignals in parallel
both to the bridge for null and to the amplifier,
varying the Pulser output will have no effect on the
null if perfect amplifier linearity is assumed.
As an ex ample of this method, assume that the
amplifier under test has essentially zero output
impedance. Set R1 equal to 100Ùand R2 equal to
200Ù. Let diodes D1 and D2 be 2N2048 connected
as diodes. Only one-half of the actual amplifier
output voltage can be measured directly at point A
due to the superposition of the outputs of the Pulse
generator via R1 and the amplifier via R2. To specify
nonlinearity as a percentage of full Output voltage,
the calibration of 10 mV/cm will be equal to 10 mV/5
V or 0.2% per cm. Therefore it is seen that 0.1% is
quite easily resolved.
In addition to linearity measurements, it is obvious
that this method can be quite useful in
measurements of temperature stability.
Pulse Height Analyzer Calibration With the
Pulser calibrated to read directly in terms of energy
as described earlier in this section, the calibration of
a complete spectrometry system from preamplifier
to multichannel analyzer, i.e., analog to digital
converter (ADC), can readily be accomplished by
simply feeding into the preamplifier a calibrated
energy signal and observing the corresponding
channel into which it is assigned by the ADC.
An important consideration in this test involves
ensuring that the linear system "goes through zero,"
and that the output of the pulse generator is properly
terminated. The attenuator switches in the 480 have
an accuracy controlled by 1% metal film resistors
and could be used to digitally check the linearity of
the spectrometer. In addition to the attenuator
accuracy, the Pulse Height control has independent
integral nonlinearity of ±0.25%. This control
therefore allows an integral linearity curve of the
ADC to be taken over the continuous range of the
ADC, i.e., from zero to the maximum address of the
ADC. Due to the better integral linearity control,
continuous scanning with the Pulse Height control is
the recommended method of checking for system
linearity. The linearity of the ADC can therefore be
determined by having previously taken the linearity
curve of the amplifier and preamplifier as outlined
earlier in this section.
5. MAINTENANCE
5.1. TESTING PERFORMANCE OF THE
PULSER
The following information is intended as an aid in
the installation and checkout of the 480. These
instructions present information on front panel
controls, waveforms at test points, and output
connectors.
The following, or equivalent, test equipment is
needed:
Tektronix Model 580 Series Oscilloscope
100ÙBNC Terminators
Vacuum Tube Voltmeter
Before testing the performance of the 480, take the
following preliminary steps:
1. Visually check the module for possible damage
due to shipment.
2. Connect ac power to NIM-standard Bin and
Power Supply, 0RTEC 401 /402.
3. Plug module into Bin and check for proper
mechanical alignment.
4. Switch ac power on and check the dc Power
Supply voltages at the test points on the 402.
The performance test consists of the following:
1. Set the front panel controls on the 480 as follows:
a. relay switch to On,

8
b. polarity switch to Pos,
c. Cal set to full clockwise and Pulse Height
control to 1000,
d. all Attenuator switches set to X1 position,
e. Direct Output terminated in 100Ùand kept
terminated in 100Ùthroughout the test.
2. Apply power to the Bin and listen for running of
the mercury relay, which will be characterized by a
low frequency hum (50 or 60 Hz).
3. Set the relay switch to Off. Measure the dc
voltage from the wiper of the Pulse Height switch on
the rear panel to ground. It should be greater than 9
V.
4. Dial the Cal control fully counterclockwise and
again measure the dc voltage from the wiper of the
Pulse Height switch to ground. It should be less than
4 V. Turn the Cal control clockwise until the voltage
is 10 V.
5. Set the relay switch to On.
6. Measure the pulse at the direct output test point
TP1.
The pulse amplitude should be between the limits of
4.0 and 6.0 V. The, pulse rise time (10-90%) should
be less than 10 nsec; the pulse fall time to one-half
of its maximum amplitude should be between 230
and 290 ìsec. Do not remove the 100Ùterminator
from the Direct Output.
7. Terminate attenuated output with 100Ù. Measure
the pulse at the attenuated Output test point. The
pulse amplitude should be between the limits of 4.0
and 6.0 V. The pulse rise time (10-90%) should be
less than 10 nsec; the pulse fall time to one-half of
its maximum amplitude should be between 110 and
150 ìsec.
8. Adjust the Pulse Height dial for a Pulse of 800 mV
at the attenuated output test point. As the Attenuator
switches are switched in, the output pulse should be
between the following limits:
9. Set the Polarity switch to Neg. There should be
no change in amplitude from the Pos position.
Observe the output with a sweep of 5 msec/cm and
look for "skipping" or other erratic behavior of the
relay.
5.2. ADJUSTMENT OF DECAY TIME OF
OUTPUT PULSE
As the 480 is normally supplied, the decay time of
the output pulse is essentially fixed. The output
Pulse will decay with the time constant of 400 ìsec
if the Attenuated output only is terminated in 100Ù
and will decay with a time constant of approximately
200 ìsec if both the Direct and Atten Outputs are
terminated. In the event that a time constant shorter
than 200 ìsec is desired, it is necessary to parallel
a fixed resistor from the normally open contact of the
mercury-wetted relay to ground. The value of this
shunting resistor will depend upon the exponential
time constant desired. The addition of this resistor
should physically be in close proximity to the actual
relay; that is to say, the resistor should be added
directly onto the etched circuit board. Decay time
constants as short as 10 ìsec can be accomplished
quite easily.
5.3. TABULATED TEST POINT VOLTAGES
The following voltages are intended to indicate the
typical dc voltages measured on the etched circuit
board. In some cases the circuit will perform
satisfactorily even though due to component
variations there may be some voltages that measure
outside the given limits. Therefore the voltages given
should not be taken as absolute values, but rather
are intended to serve as an aid in troubleshooting.
All voltages are measured from ground with dvm
having input impedance of 10 MÙor greater.
Polarity switch set to Neg.

9
5.4. SUGGESTIONS FOR
TROUBLESHOOTING
In sit uations where the 480 is suspected of
malfunction, it is essential to verify such malfunction
in terms of simple pulse generator impulses at the
output. In consideration of this, the 480 must be
disconnected from its position in any system, and
routine diagnostic analysis performed on the Pulser
with a vacuum tube voltmeter and oscilloscope. It is
imperative that testing not be performed with any
amplifier system until the Pulser performs
satisfactorily by itself. The testing instructions of
Section 6.1 of this manual and the circuit description
in Section 5 are intended to provide assistance in
locating the region of trouble and repairing the
malfunction. The guide plate and shield cover can
be completely removed from the module to enable
oscilloscope and voltmeter observations with a
minimum chance of accidentally short circuiting
portions of the etched board.
The 480 may be returned to ORTEC for repair
service at nominal cost. Our standard procedure
requires that each repaired instrument receive the
same extensive quality control tests that a new
instrument receives. Contact our Customer Service
Department, [phone], for shipping
instructions before returning an instrument.

10
Pin Function Pin Function
1 +3 V 23 Reserved
2 - 3 V 24 Reserved
3 Spare bus 25 Reserved
4 Reserved bus 26 Spare
5 Coaxial 27 Spare
6 Coaxial *28 +24 V
7 Coaxial *29 - 24 V
8 200 V dc 30 Spare bus
9 Spare 31 Spare
10 +6 V 32 Spare
11 - 6 V *33 117 V ac (hot)
12 Reserved bus *34 Power return ground
13 Spare 35 Reset (Scaler)
14 Spare 36 Gate
15 Reserved 37 Reset (Auxiliary)
*16 +12 V 38 Coaxial
*17 - 12 V 39 Coaxial
18 Spare bus 40 Coaxial
19 Reserved bus *41 117 V ac (neutral)
20 Spare *42 High-quality ground
21 Spare G Ground guide pin
22 Reserved
Pins marked (*) are installed and wired in
ORTEC’s 4001A and 4001C Modular System
Bins.
Bin/Module Connector Pin Assignments
For Standard Nuclear Instrument
Modules per DOE/ER-0457T.